What I've sometimes done when I've needed a second level quote, or needed to both quote the parent comment and something else, is use a code block but word wrap it at some length hopefully not too wide for mobile.

Here is an example using blocks wrapped to 40. How is this on mobile?

>This is a top level quote

  second level quote something about the
  quick brown fox jumped over the lazy
  poodle

    third level quote the fox was Scottish
    and wearing a kilt, and nothing else.

      fourth level quote when he jumped over
      the poodle she saw his junk and
      complined to HR

        fifth level the fox got in trouble for
        harassement, and the poodle got in
        trouble for cultural insensitivity to
        Scots

          sixth level also the company got in
          trouble with OSHA for putting the
          poodle's workstation in a place where
          others had to jump over her to get in
          and out of the building